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arm64: Turn on KPTI only on CPUs that need it

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commit 0ba2e29c7f upstream.

Whitelist Broadcom Vulcan/Cavium ThunderX2 processors in
unmap_kernel_at_el0(). These CPUs are not vulnerable to
CVE-2017-5754 and do not need KPTI when KASLR is off.

Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Jayachandran C <jnair@caviumnetworks.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Alex Shi <alex.shi@linaro.org> [v4.9 backport]
Signed-off-by: Mark Rutland <mark.rutland@arm.com> [v4.9 backport]
Tested-by: Will Deacon <will.deacon@arm.com>
Tested-by: Greg Hackmann <ghackmann@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jayachandran C
2018-04-03 12:09:18 +01:00
committed by Greg Kroah-Hartman
parent f93aea3da2
commit 2adcb1fb38
1 changed files with 7 additions and 0 deletions
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7
arch/arm64/kernel/cpufeature.c
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@@ -766,6 +766,13 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry,
if (IS_ENABLED(CONFIG_RANDOMIZE_BASE))
return true;
/* Don't force KPTI for CPUs that are not vulnerable */
switch (read_cpuid_id() & MIDR_CPU_MODEL_MASK) {
case MIDR_CAVIUM_THUNDERX2:
case MIDR_BRCM_VULCAN:
return false;
}
/* Defer to CPU feature registers */
return !cpuid_feature_extract_unsigned_field(pfr0,
ID_AA64PFR0_CSV3_SHIFT);